The U.S. Census Bureau said Tuesday it has asked its inspector general to look into a New York Post report that national employment data ahead of the 2012 election were manipulated.

The bureau says it does not believe any improper conduct was widespread or had any impact on the reported unemployment rate.

"We have no reason to believe that there was a systematic manipulation of the data described in media reports," Census said in a statement. "We carefully cross check and verify the work of our staff to ensure the data's validity."

Meanwhile, the House Committee on Oversight and Government Reform has launched its own investigation.

In the New York Post Tuesday, columnist John Crudele wrote that a sharp drop in the jobless rate in September 2012, from 8.1% to 7.8%, may have been caused by one or more Census employees fabricating responses to the bureau's monthly survey. The unemployment rate is calculated by the Labor Department based on the Census survey of 60,000 households.

The September 2012 report, released Oct. 5, was eagerly anticipated because it was one of the final ones before the presidential election and may have shaped voters' opinions about President Obama's handling of the economy.

In September of last year, the number of Americans who said they had a job jumped by 873,000, an unusually high number, causing the jobless rate to fall dramatically.

The Post column quoted one former household-survey employee in the Philadelphia region, Julius Buckmon, who admitted fabricating data in 2010 under pressure from a supervisor. Census workers are required to reach 90% of the households they identify and report on their job status, according to the Post column. When Buckmon fell short of that goal, a manager told him to make up responses from imaginary households to close the gap, he told the Post.

Although Buckmon told the Post he wasn't instructed to report those survey respondents as being employed, the Post quoted other unnamed individuals as saying that concocting respondents would have increased the total of employed Americans.

Buckmon worked at Census from December 2002 to August 2011, the agency says. Survey takers, it says, have been caught fabricating responses from time to time. They are swiftly disciplined, Census says, and the incidents are routinely referred to the inspector general of the Commerce Department, which houses Census.

Such incidents, it says, occur in fewer than 1% of all cases and would not affect the jobless rate, noting that about 7,000 Census workers in six regions conduct the interviews that contribute to the survey.

In a statement, the Commerce Department's Office of Inspector General said: "We are aware of the media reports and our office is evaluating what action may be warranted."

Separately, in a letter to Census Bureau Director John Thompson, the leadership of the House oversight committee calls the allegations "shocking."

"If true, there may be a systemic problem that the Philadelphia Regional Census Office, where the alleged data fabrication occurred," says the letter by committee Chairman Darrell Issa, R-Calif.; Blake Farenthold, R-Texas, chairman of the subcommittee on the Census; and Kevin Brady, R-Texas, chairman of the Joint Economic Committee. "The implications of an unreliable unemployment figure are serious and far-reaching."

Gus Faucher, senior economist at PNC Financial, says, "If the data are being manipulated, that's a big concern" because economists rely on it to provide a portrait of the labor market and the economy.

But he says the household survey reports have been consistent with other data �such as jobless claims reports � that point to a slowly improving employment market.